Plural stage impact breaker with impacting rotors and adjacent deflector screen grates



Oct. 23, 1956 A. B. HANSE ET AL 2,767,928

PLURAL STAGE IMPACT BREAKER WITH IMFACTING ROTORS AND ADJACENT DEFLECTCR SCREENGRATES Filed Dec. 18, 1950 v 3 Sheets-Sheet 1 l INVENTORS.

Qlbe'ri i3. flanae,

BY fled Oct. 23, 1956 A. B. HANSE ET AL 2,757,923

PLURAL. STAGE IMPACT BREAKER WITH IMPACTING ROTORS AND ADJACENT DEFLECTOR SCREEN GRATES 3 Sheets-Sheet 2 Filed Dec. 18, 1950 v INVENTORS.

.Bfihnse ert Z3 3 4 w 1 n 3 A c E Q r. 3 E I rill} a -I r I- H r 1H H. .w l-: h 1 P Ll: F j 3 a w a.

Oct. 23, 1956 A. B. HANSE ET AL 2,767,923

PLURAL STAGE IMPACT BREAKER WITH IMPACTING ROTORS AND ADJACENT DEFLECTCR SCREEN GRATES Filed Dec. 18, 1950 3 Sheets-Sheet 3 1Z7 QQ VER T107 1 IN VEN TORS. CZZberif). fiiz-nse, BY Fred United States Patent PLURAL STAGE INIPACT BREAKER WITH 1N1- PACTING ROTORS AND ADJACENT DEFLEC- TOR SCREEN GRATES Albert B. Hanse and Fred W. Rollins, Cedar Rapids, Iowa, assignors to Pettibone Mulliken Corporation, Chicago, 111., a corporation of Delaware Application December 18, 1950, Serial No. 201,364

12 Claims. (Cl. 24186) In breaking up large rocks, it has long been recognized that one of the most efiicient methods of breaking the rocks comprises impact breaking. Typically, the large rock is dropped into the path of a rotating hammer, which strikes the rock with sutficient speed to shatter it. A number of different impact breakers have been provided. Nevertheless, impact breakers have not, prior to the present invention, reached the potential attainable with this invention. The present invention provides various improvements for increasing the efliciency and effectiveness of impact breakers and in some respects, is suitable for use with other breakers as well.

According to one of the features of the invention, the rock, upon being impacted by the hammer and shattered, is thrown toward a deflector screen grate or grid having its bars disposed with their length lying in vertical planes. This disposition of the bars (compared to horizontal bars) allows a larger percentage of the rock fragments which have been reduced to the desired size to pass through the grid and drop out of the breaker without the wastage. of power that would be attendant upon retaining them within the breaking zone, where they would again be struck by the hammers.

According to another feature of the invention, the bars of this grid are so disposed that the rock fragments which are too large to pass through the grid are, for the most part, ricocheted upwardly by the bars, so that they tend to drop at a good speed well clear of the grid to be struck again by the hammers at an efficient position.

Another feature of the invention provides for controlling the path of the incoming stream of fresh rock so as to adapt the path to the type of incoming rock so that the hammers will strike it in the zone which is most suitable for that rock.

A final grating provided beyond the stripper bar also includes novel features. The portion of it against which rock is likely to be thrown by impact of the hammers on the rock includes vertically-disposed bars with the abovementioned advantage. The whole grating is mounted'in a simple manner which facilitates adjusting its tension and also facilitates adjustment of it for clearance with respect to the circle of movement of the hammers.

According to another feature of the invention, improved wedging action is provided, all wedges being assured of a full bearing on the wedged parts by virtue of a self-aligning feature which enables one of the wedged parts to rock about a cylindrical bearing surface to accommodate itself to the wedge. This wedging construction has been found to provide the wedged parts with a high degree. of dependability as well as relative ease in application.

Additional objects and advantages will be. apparent from the following description and from the drawings.

Designation of figures Figure 1 is a perspective view of a rock breaker, built in accordance with the present invention and which has been chosen for illustration thereof.

ICC

Figure 2 is a longitudinal, vertical, cross-sectional view taken, for the most part, approximately through the middle of the structure of Figure 1.

Figure 3 is a fragmentary, approximately vertical, sectional view, taken near the line 33 of Figure 2 and showing particularly the face of the main deflector screen grate.

Figure 4 is a fragmentary view on a larger scale, showing the wedging features for holding a hammer in place.

Figure 5 is a sectional view taken approximately on the line 5-5 of Figure 2, showing particularly the construction and mountingv of the stripper bar and its tensioning means.

Figure 6 is a fragmentary side view of the structure shown in Figure 5, being taken approximately on the line 6-6 of Figure 5, the parts being shown slightly tilted in a clockwise direction, so that the parts may be positioned as projections of. like parts in Figure 5, for greater clarity.

Figure 7 is aface view of the lower grating.

Although the law requires setting forth the prepared form of the invention and the inclusion of a full and exact description of at least one form of the invention, such as'that which follows, it is, of course, the purpose of a patent to cover each new inventive concept therein no matter how it may later be disguised by variations in form or additions of further improvements; and the appended claims are intended to accomplish this purpose by particularly pointing out the parts, improvements, or combinations in which the inventive concepts are found.

General operation The form of the invention chosen for illustration is seen generally in Fig. 1. The internal structure is seen generally in Fig. 2. Large rocks are fed to inclined slide 11 and slide from this slide into the circle of rotation of a rotary hammer assembly 12. Here the rock is struck by one of the hammers 13, which shatters or fractures the rock and throws the pieces toward grid 14, composed mainly of spaced bars 16 in vertical planes. Most of the pieces which are small enough pass through the grid 14 and fall through the discharge area 17. Usually a conveyor is. provided. below the illustrated apparatus to receive the broken rock and carry it to a vibratory screen. The larger pieces of fractured rock will strike the bars 16 and usually be deflected upwardly and inwardly to drop clear of grid 14 and be struck by the hammers, sometimes being broken by this impact.

The bars 16 preferably have faces flat transversely and curved longitudinally, as shown, about a point a little above the zone of impact of fresh rock with rotary hammer. Accordingly, many of the rock fragments will ricochet upwardly and rearwardly, so that they will drop back into one of the hammer circles of hammers 13 and 20, at a sufficient speed so that many fragments will be struck by the faces of hammers 13 instead of their corners. Particles are blocked from flying out of the breaker by cur tains formed of chains 18. Flying dust may be reduced by one or more curtains 19, which may be formed of reinforced rubber, such as conveyor belting. If desired, laterally overlapping strips of belting, each hung from the top in the manner of chains 18, may be used in place of chains. Some of the rock which does not pass through grid 14 will fall onto a second rotary hammer 20, which will again shatter it, most of the pieces flying against or through grid 14.

Adjustable slide The slide or chute 11 is preferably adjustable in angularity to shift the course of the incoming rock. In this Way, the direction toward which the fragmented pieces are thrown by the hammers can be controlled to give the best results with different types of rocks.

The adiustability is accomplished by supporting the slide or chute 11 on arcuate brackets 21, the brackets preferably being welded to the slide 11. The bottom edge 22 of the brackets 21 is arcuately shaped with the top centered approximately about the guide 11, so that the whole structure may shift about this top edge. Support blocks 23, carried by the frame of the breaker, are correspondingly shaped along their upper faces to give movable support to the brackets 21. Once adjusted, the brackets 21 are held firmly in place by bolts 24, each of which extends through a slot in the brackets 21, and by clamp plates 26 which may be tightened against the brackets 21 adjacent the arcuate surfaces 22.

Rotary hammers The rotary hammers 12 and 20 may be identical and may therefore both be described with reference to rotary hammer 12. A rotor 27 is carried by a shaft 28, which is rotatably supported at opposite ends by bearing blocks 29, one of which is seen in Fig. 1. Each end of the shaft may carry a multiple V pulley 31 for V-belts, connecting it either with a motor or with the shaft 32 of rotary hammer 20. It is desirable for the hammers to be jointly driven, so that the entire power available from the motor and from momentum will be behind every impact.

Each rotor 27 is provided with three slots along its length, in each of which a hammer 13, extending the length of the rotor 27, is positioned. As seen best in machining by rockably mounting the hammer 13 with respect to the rotor 27. Thus the hammer 13 and rotor 27 are provided with correspondingly shaped cylindrical surfaces 36, positioned to lie directly opposite the midzone of the wedge 33 in the expected position of the wedge. It will be observed that the hammers 13 are reversible so that when one side thereof, which is exposed, has been excessively worn, the hammer may be inverted, end for end, to expose the other side thereof, which has, until then, been protected within the rotor 27. Access for turning or placing the hammers may be had in any convenient manner. For example, a door 37 may be provided in one or both sides of the rock breaker, as seen best in Fig. 1. It will be understood that the illustrated rock breaker is of a fairly large size, the door 37 being large enough for a man to pass through, say 28" high.

Deflector screen grate The grid 14 is preferably a manganese steel casting, its details of construction being reasonably apparent from Figs. 2 and 3. It may be turned end for end as it wears, to prolong its life. It comprises mainly the parallel bars 16 supported by cross pieces 41 at top and bottom. At present, reinforcing webs 42 at the center are desired. This permits using thinner bars 16 than would otherwise be sufficiently sturdy in the lateral direction. The webs 42 are preferably set back from the face of the grid 14 so that most of the rock fragments will strike only the bars 16.

The bars 16 are preferably wider at their front faces than at their trailing faces. In other words, their walls diverge from one another rearwardly, so that rock passing the front face will pass easily through the grid instead of occasionally becoming jammed within the grid.

The grid 14 should be secured very firmly. Accordingly, it is not desired to rely on bolts 43, which bolt it to the side plates 44. In addition, the grid 14 is held by wedges 46 and 47 against liner plates 48. It will be understood that the liner plates are provided in any event throughout the main chamber in front of grid 14 for the protection of the side plates 44. The liner plates are heavy plates of manganese steel and they may be bolted to the side plates 44. Thus, various bolts 49 have been illustrated in Fig. l for securing the liner plates 48 immediately in front of grid 14. These liner plates are cut to fit the side bars 51 of the grid, and preferably one of them is notched to receive a lug 52 cast on grid 14 for supporting the grid in the proper vertical position.

Proper action of the wedges 46 and 47 is ensured by providing them with self-adjusting reaction surfaces. Thus, each of the wedges 46 bears against a backing block 53 carried by a circular plate 54, fitting a circular hole in the side plate 44, and movable therein. Wedge 47 bears on a block 56 which has shiftable arcuate en gagement with a fixed block 57 secured on the inside of a side plate 44.

In the course of assembly, the grid 14 may be lowered by a crane into position, resting on the side plates 48. The block 56 may then be placed against the block 57 and the wedge 47 applied. Next the blocks 53 are put in place, each with its plate 54, these being previously welded or otherwise secured together and being inserted in the circular holes in plate 44 from the inside of the plates 44. Retaining plates 59 are then bolted to the circular plates or discs 54 so that the discs are held in place but can turn. The wedges 46 are then inserted. When the wedges 46 and 47 have been hammered home to press the grid 14 firmly against plates 48, the various parts may be secured in place. Thus the wedges 46 and 47 Will be secured by tightening bolts 61. The block 56 may be secured by tightening bolt 62, although tightness of this bolt is not essential, except to prevent loosening by vibration. Bolts 43, which will probably have been previously loosely applied through side walls 44 and side bars 51, will now be tightened.

Stripper bar A stripper bar 66 (an assembly of parts) is positioned as seen best in Fig. l to lie close to the hammer circle of the rotary hammer 20. This stripper bar is carried in a stripper bar guide 67, which forms an opening through the side plates 44. The stripper bar assembly. at both ends, extends through the side plates. It is shiftable in guides 67 to move toward or away from the ham mer circle, the position control being described under the next heading. The form of stripper bar at present is best understood from Fig. 5. From this, it is seen that the stripper bar comprises two main parts, namely, a head 68 and a carrier 69, which latter extends through the guides 67 and side walls 44. The head 63 is pro vided with tongues 71, into which draw bolts 72 are dropped through an open-sided slot. The head and bolt assembly is then slipped into carrier 69 and drawn tight by nuts 73, which may rest on washers or an apertured plate 74. A carrier 69 may have guide lugs 76 welded thereto. A wear plate 77 (Fig. 2) may be applied to the exposed face of the carrier 69, having been omitted from Fig. 5, partly for clarity and partly because it is not deemed necessary, at least unless the rock is very abrasive.

Stripper positioning and control The position of the stripper bar assembly 66 is determined with reference to a torque tube 78, which is pivotally carried by plates 79 secured to side plates 44. The torque tube is urged by spring bars 81 in the direction of the arrow shown in Fig. 6 to turn plates 82 thereon in a direction to thrust stripper bar 66 forwardly, namely, to the left, as seen in Figs. 5 and 6. The plates 82 are welded to torque tube 78 and comprise links of a pair of toggle link systems. Thus each plate or link 82 engages a link assembly 83, which engages a pin 84 extending outwardly from the end of carrier 69. It is apparent from Fig. 6 that as the plate 82 is turned counterclockwise toward its iliustrated position, the toggle linkage comprising link 33' and plate 82 approaches alignment and the stripper bar 66 is thrust forwardly. The stripper bar is preferably placed firmly against a stop, such as shims 86, which may be inserted or removed in accordance with the desired position of the stripper bar 66. The shims 86 may be of T-shape, with the legs fitting into the slot formed by guide 67 and with the heads provided with an aperture through which a bolt 87 may pass to hold the shims in place.

The length of the toggle link 83 is preferably adjustable. This adjustment may be accomplished by wedges, but in the illustrated form it is accomplished by bolts 88. When these bolts are tightened, they clamp link plates 89 against link plate 91. Link plate 91 engages a pin 84, while link plate 89 engages plate or link 82, being pivoted thereto by a bolt 90.

The length of link 83 is adjusted to keep the toggle linkage slightly out of dead center alignment when the stripper bar 66 is thrust home. As a further safeguard to prevent the toggle linkage from swinging into alignment, an adjustable stop 92 is provided. This stop may be mounted on side plates 44 and adjusted by a screw 93, bolts 94- being tightened when it is properly positioned.

The spring bars 81 are anchored at one end to a torque ring 96 which may be secured to tube 78 by bolts 97. At their other ends, the spring bars 81 are anchored in a torque ring 98, which is held within tube 78 by bolts 99. In this instance, however, the bolts 99 ride in an annular groove 101 in torque ring 98, so that it may turn with respect to tube 78. As seen best in Fig. 1, a tensioning lever 102 is secured to torque ring 98 so as to turn this torque ring and twist the spring rods 81. The tensioning lever 102 is held in its tensioned position by a link 103 secured to the side plate 44. In making any adjustment, the bolt 104 securing lever 102 to link 103 is first removed and the lever 102 eased to its natural position to relieve the tension on the parts.

The tension can be varied by changing the number of spring bars 81. These are anchored to the torque rings 96 and 98, as seen in the cross section of ring 96 in Fig. 5. The center aperture in ring 96 is squared in cross section. In the illustrated form, it is large enough to hold 16' of the bars 81 arranged in four rows of four each. It may be assumed, however, that only four of bars 81 are illustrated, the space of the remaining twelve being occupied by filler pieces 106.

The force required for a piece of tramp iron or the like to press the stripper bar 66 outwardly depends on the number of spring bars 81 used and also on the proximity of the toggle links 82 and 83 to alignment. Hence, minor variations in the seating force applied to stripper bar 66 may be made by adjusting the length of composite links 83, the position of stop 92 preferably being changed accordingly. It is usual, however, for the stop 92 to be slightly spaced below the toggle link 83 so as to ensure firm seating of the stripper bar 66 on the shims 85.

As the toggle linkage collapses, its mechanical advantage decreases rapidly, more than offsetting the increasing spring tension, at least in the initial part of the stroke which is all that usually occurs. It is desirable for the stripper bar to move back relatively easily once it has started, and it is especially desirable for it not to increase its opposition to movement, as this wouldnecessitate setting the initial tension lower than the optimum or would fail to give the degree of protection desired.

To limit the outward movement of the stripper bar, one or more stops 103 may be provided, these stops preferably being adjustable to permit as much movement as is safe. They should protect spring bars 81 against being twisted far enough to acquire a set.

A seal plate 109 is preferably provided in conjunction with the stripper bar to seal the opening in guide 67 6 against the passage of flying dust therethrough. The plate 109 may be secured to the stripper bar carrier 69 and may slide in guidways 111.

Lower grating Beyond the stripper bar 66 a lower grating 112 is provided. This grating includes a cast frame 113, including cross pieces 114 and 116. Vertical grate bars 117 are carried by the cross pieces 114. Horizontal grate bars 118 are carried by the side members of the frame 113. Vertical grate bars 117 are preferred in at least the upper portion of this grating, perhaps extending further down than is shown. Much of the material which approaches these grate bars 117 is in the nature of flying rock fragments and those already reduced to size are less likely to strike the side faces between the bars if the bars are vertical, hence passing through better and causing less wear. For the final breaking of the residue, at least one horizontal bar 118 is more eifective, tending to restrain the passage of the oversized particles until they are struck by a hammer.

The side portions of frame 113 have formed integrally therewith rearwardly extending lugs 121, on each of which is formed an outwardly-extending pin 122. These pins fit inholes in slide brackets 123, each of which slides on a ledge 124. The extent of inward movement of the slide brackets 123 is adjustably limited by bolts 126 threading into' a lug 127, each formed on or welded to a slide bracket 123.

The upper end of grating 112 bears against a lug 128 carried by the side of the breaker. The lug 128 may, for example, be welded to or cast on plate 129, which comprises one of the heavy protective lining plates. The grating 112 is pressed by spring assemblies 131 against the stop lug 128 and as far toward the rotary hammer 20 as is permitted by bolts 126. Each of the spring assemblies 131 includes a pressure spring 132 surrounding a pressure rod 133. The pressure rod 133 is pivoted to the grating frame 113 and slides in a cross beam 134. The tension on spring 132 may be adjusted by nuts 136 threaded to rod 133.

It will be noted that the grating 112 fioates freely except for being restrained against excessive forward or downward movement, and except for the spring loading thereof.

The arrangements of the bars 117 and 118 are best seen in Fig. 7. These bars are retained in place by plates 139, which may be bolted to frame 113 and serve additionally as wear plates.

F urzher details Various provisions may be made for reducing the amount of dust escaping from the rock breaker. For example, an adjustable plate 151 may be provided to be moved upwardly against the chute 11 after each adjustment thereof. A hopper, not shown, would naturally be secured to the bed of the rock breaker, closing the entire bottom thereof and directing the broken rock to a conveyor. A sliding shield 153 may be provided to move vertically as the pressure rod 133 is shifted to close off the slots which must be provided in the back plate for movement of this rod.

Various features may be resorted to for reducing wear. Beads of welding alloy may be applied to leading corners and other portions of the rotary hammers and rotor structures on which wear is concentrated. All bolts and nuts within the rock breaker may be countersunk and the heavy lining plates may be gradually thickened in the area surrounding each bolt to provide extra thickness for such countersinking.

The heavy protective plates are preferably provided wherever the walls of the breaker are exposed to severe wear. In some instances, it is more practical to use the heavy plate as the sole wall member rather than as a replaceable liner. A special casting 154 (Fig. 2) may be 7 provided at the bottom of the entrance hood 156. In addition to receiving impacts of fragments thrown directly from the rotor, it may be struck by the upper corners of the largest incoming rocks and its bottom will be struck by pieces ricocheting from the bars 16, especially pieces thrown against them by the second rotary hammer 20.

The discharge passage behind grid 14, stripper bar 66 and grating 112 is preferably wide and unobstructed, as shown. The various demarcations shown therein in Fig. 2 are all as shallow as the thickness of plates 43, so that even clay is not likely to accumulate and clog.

As stripper head 68 wears, it may be turned over for longer life.

It will be observed that the rock, both fresh rock and fragments which fall with it, follows a nearly radial course into the path of the hammers 13, as has long been recognized to be desirable.

The provision of bars in the main grid 14 which lie predominantly in planes perpendicular to the axes of the rotors allows a larger percentage of rock fragments which have already been reduced to size to pass through the grid. This results from the fact that the angularity of approach of the rock fragments toward the grid is considerably wider in this plane than in planes parallel to the axes. This is especially true of a plurality of hammer rotors, because the starting points of the rock fragments from the two rotors is so widely separated.

The subject matter described under the heading Strip per Positioning and Control" is claimed in a continuing application filed before issue of this patent, Serial No. 550,439.

We claim:

1. An impact rock breaker, including rotary hammer means, means for directing rock to be broken into the path of the hammer means at a predetermined impact zone, and a plurality of bars against which the fragmented rock is thrown by the hammer, said bars being disposed above the hammer means and generally vertically in parallel relationship, with the length of the bars lying in planes perpendicular to the rotary axis of the hammer, and the front faces of the bars struck by the fragmented rock being curved concavely toward the impact zone.

2. A rock breaker including a rotary hammer, a grating facing said hammer and means for yieldably mounting said grating, including stop means for positioning the end of the grating first approached by the hammer, slide means for slidably supporting the other end of the grating for movement toward and from the rotary hammer, spring means for urging the grating in a direction toward the stop and toward the hammer with floating yieldability permit ting movement away from the hammer at any point of the grating and adjustable means for limiting the movement of the slide means toward the hammer.

3. A rock breaker including a housing, a hammer within the housing, a grid structure against which the hammer throws rock fragments, a protective lining for the housing secured to the side walls thereof and extending only part way along the walls, and means wedging the grid against the edge of the protective lining to secure the grid rigidly in place, said means including a wedge and a rockable backing member positioned to receive the wedge between it and the grid and adapted to rock to accommodate itself to the wedge.

4. An impact rock breaker, including a rotary hammer, means for directing rock to be broken into the path of the hammer at a predetermined impact zone, and a plurality of bars against which the main stream of fragmented rock is thrown by the hammer directly from said zone, said bars being parallel with their length generally lying in planes perpendicular to the axes of the rotary hammer, with their front faces curved approximately about a point in the path of the rock approaching the hammer, said bars being of reducing width rearwardly, and said means for directing the rock including a slide down which the rock 8 passes, and adjustable support means for adjustment of the inclination of the slide to shift the impact zone.

5. An impact type rock breaker including a housing having feed and discharge openings, rotary hammer means in the housing, means for rotating the hammer in a given direction, said hammer being spaced from a wall toward which the upper part of the hammer moves, the spacing providing a discharge passage, feed means for dropping rock over a member parallel to the hammer axis and ap proximately radially into the hammer circle along the axial length of the hammer to be crushed by free impact of the hammer from which it will be thrown mainly along a predetermined trajectory path approximately perpendicular to the line of feed, and screening means directly in said path, and widely spaced from the hammer means and entirely above the level of hammer means where the hammer means approaches nearer to the screen to avoid pinching rock between the screen and the hammer, extend ing substantially entirely across said path and having openings aligned with said path to allow smaller fragments of rock to discharge after the first hammer impact, while retaining larger pieces for further breakage, said screening means comprising bars of a thickness parallel to said path greater than their width perpendicular to said path; the spaces between the bars all opening at their rear directly to the discharge passage.

6. An impact type rock breaker including a housing having feed and discharge openings, a rotary hammer in the housing spaced from a wall toward which the upper part of the hammer moves, the spacing providing a discharge passage, feed means for dropping rock over a member parallel to the hammer axis and approximately radially into the hammer circle along the axial length of the hammer to be crushed by free impact of the hammer in a zone from which it will be thrown mainly along a predetermined trajectory path approximately perpendicular to the line of feed, and screening means directly in said path, widely spaced from the hammer to avoid pinching rock against the hammer, extending substantially entirely across said path and having openings aligned with said path to allow smaller fragments of rock to discharge after the first hammer impact, while retaining larger pieces for further breakage, a second rotary hammer positioned beneath said path to strike and crush by free impact of the hammer fragments dropping after being retained by said screening means; the openings of said screening means all opening at their rear directly to the discharge passage.

7. An impact type rock breaker including a housing having feed and discharge openings, a rotary hammer in the housing spaced from a wall toward which the upper part of the hammer moves, the spacing providing a discharge passage, feed means for dropping rock over a member parallel to the hammer axis and approximately radially into the hammer circle along the axial length of the hammer to be crushed by free impact of the hammer in a zone from which it will be thrown mainly along a predetermined trajectory path approximately perpendicular to the line of feed, and screening means directly in said path, widely spaced from the hammer to avoid pinching rock against the hammer, extending substantially entirely across said path and having openings aligned with said path to allow smaller fragments of rock to discharge after the first hammer impact, while retaining larger pieces for further breakage, a second rotary hammer positioned beneath said path to strike and crush by free impact of the hammer fragments dropping after being retained by said screening means, and a second screening means positioned in the path of material which, after being rejected by the first-named screening means has been struck by the second rotary hammer, to pass to discharge smaller fragments while retaining larger pieces for further breakage; the spacing of the openings of both screening means all opening at their rear directly to the discharge passage.

8. An impact type rock breaker including a housing having feed and discharge openings, a rotary hammer in the housing spaced from a wall toward which the upper part of the hammer moves, the spacing providing a discharge passage, feed means for dropping rock over a member parallel to the hammer axis and approximately radially into the hammer circle along the axial length of the hammer to be crushed by free impact of the hammer at a zone from which it will be thrown mainly along a predetermined trajectory path approximately perpendicular to the line of feed, and screening means widely spaced from the hammer to avoid pinching rock against the h nmer extending substantially entirely across said path having openings aligned with said path to allow smaller fragments of rock to discharge after the first hammer impact, while retaining larger pieces for further breakage, said feed means being adjustable to shift the position at which fed rock enters the hammer circle, to direct the throw of rock toward the screening means under varying conditions; the openings of said screening means all opening at their rear directly to the discharge passage.

9. A rock crusher including first and second hammer rotors, feed means for dropping rock to be broken steeply into the hammer circle of the first rotor along the length of the rotor, a first impact zone extending the length of the rotor parallel to the axis thereof, both rotors having hammers faced for rotation in the same direction, the direction being that in which the top of the first rotor moves toward the second, stationary impingement means parallel to the axis of the first rotor spaced widely from the first impact zone, and in the path of the fragmented rock thrown from the first impact zone for intercepting at least the oversize fragments of rock and dropping them mainly in a zone spaced in the direction of hammer movement from the path of unbroken rock for further breakage by the hammer rotors, a discharge passage beyond the second rotor from the feed means, and additional impingement means including a pair of screen gratings exposed at their rear to the discharge passage; a forward part of this additional impingement means, including the first of said gratings, being positioned in a path of fragments thrown from the first rotor with all of the passages within said forward portion of the additional impingement means throughout the area exposed to fragments thrown directly from the first rotor exposed at their rear directly to discharge and so aligned with the hammer circle of the first rotor that fragments as thick as the thickness of these passages can be thrown from the first rotor straight through these passages; and the second grating being positioned in a path of fragments of rocks which have been thrown from the second rotor and to receive only fragments which have passed under the forward part of the additional impingement means including the first grating; the second rotor being positioned to receive directly from the first grating oversized fragments retained by it, to impact said fragments and to throw the resulting fragments below the first grating to the second grating.

10. A rock crusher including a casing, rotary hammer rneans within the casing spaced from an end wall thereof to provide a discharge passage between the end wall and the hammer means, means for dropping material to be crushed steeply into a hammer circle of the rotor hammer means along an impact zone extending the length of the hammer means parallel to a rotary axis of the hammer circle; a first screen grating positioned in the main path of fragments thrown from said impact zone, having substantially its entire rear face exposed directly to said discharge passage for discharge through said grating of fragments sufliciently small, and having its front face positioned to drop oversize fragments into a secondary impact zone extending the length of the hammer means parallel to said axis and positioned closer to the discharge passage than the first-mentioned impact zone, said secondary impact zone also being positioned so that the fragments thrown therefrom mainly pass under the first grating; a second screen grating positioned in the path of fragments thrown from the secondary impact zone, having its rear face exposed to the discharge passage and having its front face positioned to again return the oversize fragments to the hammer means.

11. An impact rock breaker according to claim 1, in which the bars are disposed at an angle to deflect upwardly fragments thrown against it from the impact zone.

12. An impact-type rock breaker including a housing having feed and discharge openings; rotary hammer means in the housing spaced from a wall toward which the upper part of the hammer means moves the spacing forming a discharge passage, feed means for dropping rock over a member parallel to the hammer axis and directing it approximately radially into the path of the hammer means along the axial length of the hammer means to be crushed by free impact of the hammer means in an impact zone from which it will be thrown mainly along a predetermined trajectory path approximately perpendicular to the line of feed, and screening means having a bar-like screening area directly in said path, steeply inclined to cause rebounding therefrom, widely spaced from the hammer means and steeply angled with respect to the nearest part of the path of the hammer means to avoid dragging rock by the hammer means along the screening area, extending substantially entirely across said path, exposed substantially throughout its rear directly to said passage and having openings all substantially fully aligned with said path to allow smaller fragments of rock, of thicknesses up to the thickness of the openings, to pass straight to discharge after the first hammer impact, while retaining larger pieces for further breakage, said rotary hammer means rotating under the entire zone between the feed means and the screening means through which the fragments retained by the screening means drop.

References Cited in the file of this patent UNITED STATES PATENTS 1,660 Lukens et al June 27, 1840 40,072 Whelpley Sept. 22, 1863 72,418 Powell Dec. 17, 1867 198,993 Moore Jan. 8, 1878 696,628 Dickson Apr. 1, 1902 781,748 Smith Feb. 7, 1905 843,428 Ancel Feb. 5, 1907 945,160 Goetz Jan. 4, 1910 1,085,638 Shelton Feb. 3, 1914 1,152,141 Boero Aug. 31, 1915 1,185,620 Blum June 6, 1916 1,214,558 Liggett Feb. 6, 1917 1,253,547 Velde Jan. 15, 1918 1,691,951 Alfred Nov. 20, 1928 2,287,799 Hartshorn June 30, 1942 2,373,691 Kessler Apr. 17, 1945 2,471,068 Kerper May 24, 1949 2,478,733 Wright Aug. 9, 1949 2,482,279 Lemmon Sept. 20, 1949 2,486,421 Kessler Nov. 1, 1949 2,505,674 Knight Apr. 25, 1950 2,514,111 Wilson July 4, 1950 2,555,879 Fogle June 5, 1951 FOREIGN PATENTS 2,954 Great Britain July 20, 1876 7,543 Great Britain Mar. 26, 1910 

